Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/10/2009
Publication Date: 6/1/2009
Citation: Goenaga, R., Irizarry, H., Irish, B. 2009. TARS Series of Cacao Germplasm Selections. HortScience 44(3):826-827. Interpretive Summary: World average cacao yield is low. To increase yield it is highly recommended that cacao be propagated through the use of controlled-pollinated seed obtained from crosses of two or more productive parental clones. The use of hybrid seed is considered the simplest and cheapest method of cacao propagation and may offer the opportunity to assemble into a single tree useful traits from distant parents. In most cases, however, the data available to support the high yielding assumption attributed to controlled-pollinated seed is based only on the production obtained from a few segregating trees and without validation from long-term experiments. During a four-year evaluation/period at three locations we obtained individual tree yield data from about 1,320 trees originated from five single crosses. Scionwood of 40 high-yielding trees representing all crosses and locations, and scionwood of five parental trees used in the development of the crosses were grafted onto a common rootstock. The 40 selections were compared for yield with the five parents in replicated plots during a four full-year evaluation period. The results indicated that of the 1,320 initial trees observed in all populations and locations only nine trees were superior yielders with a mean production of 2,170 kg/ha/year of dry beans. A description of organoleptic characteristics demonstrated wide diversity in flavor characteristics among the nine high yielding clones. Results from this study suggest that the use of hybrid seed should be avoided in cacao propagation and substituted with grafting of superior clones onto a compatible rootstock. Genetic material of this release was deposited in the National Plant Germplasm System where it is now available for research purposes, including development and commercialization of new cultivars.
Technical Abstract: An experiment with 40 Theobroma cacao L. clones grafted onto a common rootstock was established between September 1991 and November 1997 to determine the yield potential of trees selected from interclonal families. Scionwood of 40 promising trees selected from among 1,320 trees, representing five families and three locations in Puerto Rico, were patchbud grafted onto the rootstock clone EET-400. Additionally, scionwood of five of the eight parental clones involved in the combination of the families were also grafted onto the same rootstock. The 45 treatments were arranged in a randomized complete block design with six replications, each containing two experimental trees. The trees reached full production in 1994, during the third growing year. Between 1994 and 1997 the mature pods were harvested, and the dry bean weight and pod index were determined. The means were compared with the combined means of five parental clones and the mean of the highest yielding parent. At the termination of the experiment in November 1997, only nine of the grafted clones significantly out yielded their parents with a mean production of 2,170 kg/ha/year of dry beans. This indicated that less than 1% of the trees in the original population from the five families were superior yielders. A description of organoleptic characteristics demonstrated wide diversity in flavor characteristics among the nine high yielding clones. Four of the nine superior yielding clones also had a significantly lower pod index. In 2002, scionwood of these nine clones was grafted onto Amelonado rootstock and trees established at the USDA-ARS cacao collection in Mayaguez, Puerto Rico. Budwood and seed samples of these clones were deposited in the National Plant Germplasm System where they are now available for research purposes, including development and commercialization of new cultivars.